The present invention relates to a plant-growing method and apparatus for growing a plant and more particularly to an improved method and apparatus for growing nursery stock planted in above-ground containers. Numerous methods for growing nursery stock to desired transplantation size have been utilized for years, including growing of nursery stock in above-ground containers and in the ground prior to transplanting.
The most widely used method of growing and producing relatively large sized landscape plants, e.g., trees and shrubs, is field growing. Millions of plants are planted in the field each year by growers with the intent to market the resulting grown plants several years later. For example, the number of small oak trees the grower plants in 1994 is governed by the number of grown oak trees, with 3" trunk diameter, standing 15 feet tall he estimates he can sell in 1998. The efficient grower wants to maximize his full capabilities. Therefore, the ultimate plan is to plant and grow the number of plants, of each species, the grower can sell several years later. Of course, accurately judging this futures market is a very difficult task, and consequently, many plants are grown and ready for sale with no ready market.
The plants are dug from the field after growing to the desired sale size. Most plants are dug using the ball and burlap method, either by hand or machine. An earth-root ball is formed and wrapped in burlap to hold the ball together. Wire baskets are also put around the ball to further secure it in handling and shipping until the plant is sold.
The time frame from digging to sale date always varies from days, weeks to many months. All during the time from digging the relatively large plants until they are ultimately replanted in a landscape situation, the plants must be properly cared for. The foremost consideration is keeping the root balls securely intact and providing sufficient water to the plants. It is during this time period when the plants have limited root systems with limited reservoirs for nutrients and moisture that they are most subject to stress.
The most common method heretofore employed in an attempt to accomplish the required plant care has been to place the plants in holding bins where the root balls are surrounded and covered by some type of mulching material (sawdust, wood chips, etc.) The mulching material holds the moisture and prevents drying of the root balls. The primary problems associated with this practice are that the burlap rots away and the root ball begins to deteriorate necessitating reburlapping with new material to hold the root balls together, and when the plants come out of dormancy (springtime), the leaves, stems and roots start new growth. The new root growth extends out of the root balls into the surrounding soil or growing media, and when the plants are removed from the soil or media the new root growth is lost causing the plants to suffer shock which leads to poor transplantation results.
Methods of growing nursery stock in the ground prior to transplanting such nursery stock whereby the root growth is confined in a porous fabric container are disclosed in U.S. Pat. No. 4,574,522 issued to Reiger et al., on Mar. 11, 1986, U.S. Pat. No. 4,888,914 issued to Reiger on Dec. 26, 1989, U.S. Pat. No. 5,103,588 issued to Reiger on Apr. 14, 1992, and U.S. Pat. No. 5,167,092 issued Dec. 1, 1992, to Reiger. In accordance with those methods, nursery stock, e.g., a seedling tree is confined within a porous fabric container and planted in the ground within the container. The porous fabric container has sufficient strength to restrict the root but does not completely stop penetration. The bag root prunes by choking or girdling the root as it passes through the fabric. Root growth outside the container by those roots penetrating the fabric is limited and enlarged root nodule formation and root branching take place within the fabric container. The roots that do penetrate the fabric and go into the surrounding soil bring in moisture, nutrients and help anchor the tree. Upon transplanting the nursery stock, the fabric container and nursery stock are unitarily removed from the ground and the restricted root growth outside the fabric container readily breaks off. When transplanted, the fabric container is removed from the root ball and the root ball is placed in the ground. Because of the nodule formation and root branching which took place in the fabric container, the root structure rapidly establishes itself anchoring the plant and allowing it to intake moisture and nutrients.
While the methods of the above-described patents are very useful and successful in growing nursery stock for transplantation, growing of nursery stock, such as trees and the like, in above-ground pots or boxes has been and continues to be a viable, desirable commercial practice. The root systems of plants grown in such pots or boxes are totally confined therein. Thus, as the plant reaches the desired selling or transplantation size appropriate to the size of the pot or box in which it is being grown, root circling commences. It has long been recognized that root circling leads to poor transplanting results and even eventual death of the plant. Typically, the pots utilized to grow nursery stock are plastic pots. When plants are grown in plastic pots, the plant roots hit the smooth plastic on the inside of the container and circle. Because root circling is harmful to the plant when it is transplanted from the pot, prohibiting such circling is a desired effect, and an important issue within the nursery industry. Likewise, forcing a root to prune and branch is also a desired result.
Currently, the nursery industry utilizes three methods to stop root circling and to root prune in plastic containers. The first method is an air root pruning pot. Such pots are well known in the art. With air root pruning, the root tip is killed and thus pruned, when it hits the air, and the root will begin to branch in the pot.
The second method utilized to stop root circling involves using a copper paint to line the plastic pot. When the root tips of the plant being grown in such a pot reach the copper lining, the tips are burned and killed, and thus are pruned. Root circling is thus prohibited and the roots branch in the growing medium.
The third method comprises utilizing a plastic pot with a stair step root pruning structure defined on an inner surface thereof. Such a pot is disclosed in U.S. Pat. No. 4,442,628 to Whitcomb, the details of which are incorporated herein by reference. Root tips of plants grown in such pots may be trapped in the corners of the stair step root pruning structure, so that the roots lose their apical dominance and begin to branch in the pot.
Although each of the above-referenced methods works to root prune, each has its disadvantages. A copper-lined pot will work only one time, and must be relined if it is to be utilized again as a root pruning pot. Copper can also be toxic to plants, workers and the environment if misused. The stair step pot is far more expensive to manufacture than the typical plastic pot utilized to grow nursery stock. Additionally, the stair step pot does not hold up well in use, especially during shipping and handling. The edges and joints of the stair step structure are particularly weak points. The traditional plastic pot is round and has no such joints or edges, and is therefore considerably stronger.
Air root pruning pots are also far more expensive than traditional plastic pots. In addition, because air root pruning pots are made with joints at the edges and seams, they are far weaker in use than the traditional round plastic pots. This weakness is especially evident when plants are shipped and handled in the air pruning pots. Because of these weaknesses and the expense, air root pruning pots although commonly used in the nursery industry at smaller sizes of one gallon or less, are rarely used to produce larger sized plants of three gallons or more.
Thus, there is a need for an improved method and apparatus of growing a plant in an above-ground container.